Which one among the following is not a renewable energy source?

Correct — C, Nuclear. A renewable source is one that is replenished on a human timescale and is not used up by being used. Nuclear power fails that test: it runs on uranium, an ore that has to be mined from a finite crustal stock, and every kilogram fissioned is gone. That is why India keeps nuclear power under the Department of Atomic Energy while solar, wind, biomass and small hydro sit with the Ministry of New and Renewable Energy. Nuclear power is low-carbon, which is a separate virtue, and confusing low-carbon with renewable is the mistake this question is built around.

• (a)Solar — Solar energy arrives continuously from the Sun and is not depleted by use, which makes it the clearest renewable source of the four.
• (b)Wind — Wind is driven by the uneven solar heating of the atmosphere and the Earth's rotation, so it too is continuously renewed.
• (d)Hydroelectric — Hydroelectricity is powered by the water cycle, which evaporation and rainfall keep turning; the water passing through the turbine is not consumed.

Energy resources divide into renewable and non-renewable. Renewables — solar, wind, hydro, geothermal, tidal, biomass — are replenished naturally at a rate comparable to their use. Non-renewables — coal, petroleum, natural gas and nuclear fuel — exist as fixed stocks that took geological time to form or that cannot be remade at all. A separate axis is the carbon footprint, and nuclear power sits in the unusual corner of being non-renewable yet very low in emissions.

Every candidate can name the three renewables here; the item is decided entirely by where nuclear power belongs. Two habits of mind push the wrong way. One is the association of nuclear with 'clean energy' in policy discussion, which is about emissions rather than replenishment. The other is the idea that nuclear fuel lasts a very long time, which is true but irrelevant — a large finite stock is still finite. Fusion, if it is ever made to work at scale, would change this picture; fission does not.

• Renewable sources are replenished on a human timescale — solar, wind, hydro, geothermal, tidal and biomass.
• Non-renewable sources exist as fixed stocks — coal, petroleum, natural gas and nuclear fuel.
• Nuclear fission uses uranium, which must be mined and is finite.
• Nuclear power is low-carbon but not renewable; the two properties are independent.
• In India the Ministry of New and Renewable Energy handles solar, wind, biomass and small hydro, while nuclear power falls under the Department of Atomic Energy.

• Equating low-carbon with renewable.
• Assuming a very large fuel stock makes a source renewable.
• Grouping large hydro with non-renewables because of its environmental costs.

A definition item that trades on the overlap between 'clean' and 'renewable'; sibling papers ask the same classification through exhaustible-but-renewable resources and through the basis on which resources are grouped.

• practice — not a real PYQ

  Which one of the following is a non-renewable source of energy?

  • (a)Geothermal energy
  • (b)Tidal energy
  • (c)Natural gas
  • (d)Biomass

  Answer(c) Natural gas — a fossil fuel drawn from a finite stock, unlike the other three.

• practice — not a real PYQ

  In India, solar and wind energy programmes are handled by which ministry?

  • (a)Ministry of Power
  • (b)Ministry of New and Renewable Energy
  • (c)Ministry of Coal
  • (d)Department of Atomic Energy

  Answer(b) Ministry of New and Renewable Energy — nuclear power sits separately with the Department of Atomic Energy.